High melting point calcium grease of low soap content



Patented Nov. 18, 1952 HIGH MELTING POINT CALCIUM GREASE OF LOW SOAP CONTENT Laurence F. King, Sarnia, Ontario, and Warren C. Pattenden, Courtright, Ontario, Canada, assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application June 1, 1951, Serial No. 229,548

Claims.

The present invention relates to high melting point calcium greases of low soap content. It relates particularly to lubricating greases composed substantially of mineral base lubricating oils thickened to a grease consistency with a combination of thickeners which impart better properties to the grease than have commonly been obtained in prior art compositions.

Conventional calcium base greases are widely used because of their smooth texture and their structural stability at normal temperatures. They are relatively easy to manufacture. For service at temperatures which do not exceed about 200 F. the conventional calcium base lubricating greases are quite satisfactory lubri cants. They. are relatively inexpensive because their principal ingredients are cheap. They have one well known deficiency, however, in that they commonly require the presence of a small dropping point of conventional calcium greases can be substantially raised by the addition of low molecular weight fatty acids to the usual higher fatty materials. Upon saponification of the higher fatty materials, the lower acids are converted into salts at the same time that the soap'is formed. Thus, it has been suggested in the prior art that the addition of lower acids such as acetic acid, lactic acid, and various other low molecular weight acids tends to improve the dropping point of calcium greases. Ap-

parently these acids, when co-neutralized with r the high molecular weight fatty materials, form salts with the metal base which salts in turn form a complex with the soaps. In particular it has been found possible in the prior art to prepare high melting calcium greases by saponifying with the lime mixtures of stearic acid and lactic acid, or by saponifying mixtures of 12- hydroxy stearic acid and lactic acid.

Greases prepared as just described, however, have one notable deficiency. They require a relatively large amount of the salt and soap for thickening the lubricating oil to a reasonably firm grease consistency. As will be seen in the table, below, greases of only moderate consistency made with the ingredients just mentioned may require as much as 21 to 31.5% of the combined soap and salt. Since the soap constituents are usually much more costly than the 1ubricating oil used, the use of such high proportions of thickener is expensive and therefore objectionable. Also, the high soap content makes the grease abnormally viscous at room temperatures. The harder or more viscous greases are undesirable for many purposes because, for example, they are difficult to dispense in commercial grease dispensing equipment.

The present invention is based on the discovery that greases of the general type just described can be greatly improved by replacing a part of the usual fatty acid (stearic or hydroxy stearic acid) by a partially dehydrated castor oil or fatty acid derived therefrom before saponifying with lime. Thus, a grease containing a combination of three thickening agents, namely, the calcium soap of stearic or hydroxy 'stearic acid, or of equivalent substantially saturated fatty acids having between 12 and 22 carbon atoms per molecule, the calcium soap of a partially dehydrated castor oil, and the calcium salt of a low molecular weight carboxylic aliphatic acid makes a superior product.

The partially dehydrated castor oil is preferably dehydrated by known processes until its iodine number has been increased from a normal 84, or so, to about to 110. Complete dehydration of castor oil raises the iodine number to as high a value as 118 to 140. Complete dehydration is useful for the preparation of synthetic drying oils, but for the purposes of the present invention, it is desirable that dehydration be carried out only partially to the extent indicated by an iodine value of 90 to 110, and preferably between about and 105.

As is well known in the art, castoroil can be dehydrated by heating with sulfuric acid. or phosphoric acid, or with sodium acid sulfate to carry out the dehydration to the desired extent.

The low molecular weight acid is preferably a hydroxy aliphatic acid having not more than 6 carbon atoms, for example, 3 to 6 carbon atoms. Specifically preferred acids are lactic acid, or hydracrylic acid, but any of the hydroxy butyric acids can also be used.

Preferably the three soap-forming or saltforming acidic materials, namely the high molecular weight fatty acid, or natural fat, the partially dehydrated castor oil, and the low molecular weight carboxylic acid are used in roughly equal proportions by weight prior to saponification. The invention contemplates, however, the use of as little as 1% and as much as 10% by weight based on the total grease composition of each of the three soap or salt ingredients which form the thickener. The specifically preferred compositions consist essentially of about 85 to 93% by weight of lubricating oil, 2 to 5% of the calcium soap of stearic or hydroxy stearic acid, lz-hydroxy stearic acid being specifically preferred, 2 to 5% of the calcium soap of the par- It will be understood that various conventional additives such as anti-oxidants, extreme pressure compounds, thickener agents, viscosity index improvers, and the like may be incorporated in grease compositions made according to the present invention. In general the lubricating oils preferred are of mineral base with a viscosity between 100 and 5000 S. S. U. at 100 F. and they may be of various viscosity indexes. The higher viscosity index oil, for example of 85 V. 1., or higher is particularly useful for service at widely varying temperatures with the combination of soaps and salts described herein. By the present invention, diiiiculties commonly encountered in using high V. 1. oils (because of their traditional incompatibility with soaps) are largely eliminated.

What is claimed is:

1. A lubricating grease composition comprising 70 to 95% by weight of a lubricating oil thickened to a grease consistency with 1 to by weight, based on the total composition, of calcium soap of substantially saturated fatty material of the C12 to C22 range, 1 to 10% of calcium soap of partially dehydrated castor oil, and 1 to 10% of the calcium salt of an aliphatic hydroxy carboxylic acid having not more than 6 carbon atoms per molecule.

2. Composition according to claim 1 wherein said lubricating oil is a mineral base oil.

3. Composition according to claim 1 wherein said substantially saturated fatty material is stearic acid.

4. Composition according to claim 1 wherein said substantially saturated fatty material is predominantly 12-hydr0xy stearic acid.

5. A lubricating grease composition consisting essentially of 70 to 95% by weight of mineral base oil of 100 to 5000 S. S. U. viscosity at 100 F., 1 to 10% of calcium soap of at least one fatty acid selected from the group which consists 01.

85 to 94% mineral lubricating oil 2 to 5% calcium soap of 12-hydroxy stearic acid 2 to 5% calcium soap of partially dehydrated castor oil 2 to 5% of the calcium salt of lactic acid 9. A lubricating grease composition having essentially the formula by weight:

85 to 94% mineral lubricating oil 2 to 5% calcium soap of 12-hydroxy stearic acid 2 to 5% calcium soap of partially dehydrated castor oil 2 to 5% of the calcium salt of hydracrylic acid 10. Composition according to claim 8 to which is added 0.5 to 5% of hydroabietyl alcohol.

LAURENCE F. KING. WARREN C. PATTENDEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,197,263 Carmichael Apr. 16, 1940 2,417,429 McLennan Mar. 18, 1947 2,450,219 Ashburn et a1 Sept. 28, 1948 

1. A LUBRICATING GREASE COMPOSITION COMPRISING 70 TO 95% BY WEIGHT OF A LUBRICATING OIL THICKENED TO A GREASE CONSISTENCY WITH 1 TO 10% BY WEIGHT, BASED ON THE TOTAL COMPOSITION, OF CALCIUM SOAP OF SUBSTANTIALLY SATURATED FATTY MATERIAL OF THE C12 TO C22 RANGE, 1 TO 10% OF CALCIUM SOAP OF PARTIALLY DEHYDRATED CASTOR OIL, AND 1 TO 10% OF THE CALCIUM SALT OF AN ALIPHATIC HYDROXY CARBOXYLIC ACID HAVING NOT MORE THAN 6 CARBON ATOMS PER MOLECULE. 